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Careful monitoring of insects in soybean fields and assessing how much threat they pose to crop yield could result in fewer insecticide applications and greater cost savings, says Angus Catchot, associate Extension professor of entomology and plant pathology at Mississippi State University.

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Instances of tolerance to pyrethroids

“Entomologists across the Mid-South are working on methodology for testing on bollworms in soybeans to try and get some meaningful data for growers. We generally get pretty good control of bollworms with pyrethroids, but we’re having some issues of tolerance.

“Due to issues with control in 2010, we are currently recommending mixing an Orthene with pyrethroids to improve control of bollworms. Many tests across the Mid-South have shown increased efficacy when tank mixing these products, rather than relying on a pyrethroid alone.

“Other products are available such as Belt and Steward, but when we have to start switching away from pyrethroids it’s going to get expensive. Another thing to consider is that tobacco budworms were present in soybeans last year in places in the Delta. Tobacco budworms will infest soybeans, but it’s not something we see on a regular basis. This is important because they are highly resistant to pyrethroid chemistry.”

Red-banded stink bugs were almost nonexistent last year, Catchot says, with only scattered reports of findings across the state.

“I think it was a function of the weather. I’m not expecting that we’ll see many this year — but in case, don’t confuse them with the red-shouldered stink bug. If it has a spine on the abdomen between the hind legs, it’s red-banded; if it doesn’t have a spine, but it looks similar, it’s red-shouldered. It’s important to know which you’re dealing with.”

And he cautions, when applying a fungicide, “If you don’t have bugs in the field at R-3, there is no need to include a pyrethroid with your fungicide application. When insects are not present at threshold numbers, we don’t see any yield response from just ‘adding in’ and insecticide.

“If you have a situation like this,” he told the consultants, “and you advise your grower to eliminate the pyrethroid, you’ve just paid for your services for the entire year. If there are bugs that need to be treated, by all means include a pyrethroid — but if they aren’t there, leave it out and save the money.”